1. Field of the Invention
The present invention relates to a process for removal of a polymer product in finely divided form from a viscous solution of polymer product and inert organic solvent.
2. Description of the Prior Art
Polymer products, for example, polyester resins, e.g., polycarbonate resins, can be formed by the polymerization of the appropriate monomeric reactants in an inert organic solvent. Such a polymerization reaction normally yields a viscous solution of polymer product and inert solvent from which the product needs to be isolated.
In U.S. Pat. No. 3,530,094 to H. Schnell et al., it is proposed at Col. 6, lines 44-59 that such a polymer product/inert solvent mixture be sprayed into an unstirred hot water solution to flash off the solvent with separation of the resin in finely divided form. Attempts to follow this approach have been unsuccessful since, in the absence of agitation of the hot water solution, the polymer product will form a film on the surface of the water and will not be produced in finely divided form.
U.S. Pat. No. 2,989,503 to B. P. Jibben proposes addition of the polymer product/inert solvent solution to water and a certain defined amount of dimethylbenzene, followed by evaporation of the solvent from the solution, apparently also without agitation being supplied thereto.
U.S. Pat. No. 3,842,052 to S. Gordini et al. relates to removal of hydrocarbon solvent from gummy polymers by adding a hydrocarbon solvent/polymer solution to boiling, rather than non-boiling water, with stirring.
Finally, U.S. Pat. No. 3,267,074 to N. V. Wood teaches recovery of polycarbonate polymer product from a solvent/polymer product solution by injection of the solution into a highly turbulent stream of polycarbonate non-solvent, e.g., hot water, maintained in a "shearing device". This reference at Col. 1, lines 24-52 and Col. 3, lines 7-34 specifically distinguishes a "shearing device" from a "mixing device" which is said to merely "agitate" or "mix" the components of the solution and lead to production of the product in an "undesired fibrous form", rather than a more "granular" form. The use of such "shearing" agitation, rather than the lower speed "non-shearing" or "mixing" agitation, involves the use of specialized agitation equipment and the expenditure of relatively large amounts of energy. It is not preferred for these reasons.